Inkjet printing is a well known in the art printing method. The basics of this technology are described, for example by Jerome L. Johnson <<Principles of Nonimpact Printing>>, Palatino Press, 1992, Pages 302-336. ISBN 0-9618005-2-6. Commercial products such as computer printers, large format graphics printers and others exist.
An inkjet print head consists of an array or a matrix of ink nozzles, with each nozzle selectively ejecting ink droplets. A given nozzle of the print head ejects the droplet in a predefined print position on the media. An assembly of the adjacently positioned on the media ink droplets creates a predetermined print pattern or image. Each image typically consists of multiple image elements such as pictorial or continuous tone elements, uniform tinted and solid elements, and line art and text elements. Color is another image element. Faithful reproduction of each image element is characterized by proper image sharpness, smoothness, spot size and other image quality parameters.
Inks used in the ink-jet printing industry are typically liquid solutions or emulsions. Known types of ink are oil-based inks, non-aqueous solvent-based inks, water-based inks, and solid inks. The deposited ink droplets are dried or cured. Recently, curing of ink by radiation and in particular ultraviolet (UV) radiation has become popular. In such cases, special radiation-curable ink is used and the image is cured by exposure to a curing radiation source. Typically, curing is performed by simultaneously irradiating all image elements with the same amount of curing radiation. The use of radiation-curable inks and the curing process are rapidly becoming an alternative to the established conventional drying process.
Curable ink must be cured within a short time period after it has been deposited on the substrate. Known prior art includes U.S. Pat. No. 6,457,823; U.S. Pat. No. 6,561,640 and United States Patent Application Publication No. 2004/0085423.